Merck to acquire Prometheus Biosciences for $10.8bn

Prometheus’ lead candidate, PRA023, is a humanized monoclonal antibody (mAb) in Phase 2 trials for ulcerative colitis (UC) and Crohn’s disease (CD).

Founded in 1995, the company also has a second candidate in Phase 1 trials and three others in pre-clinical development.

Phase 3 trials planned

Lead candidate PRA023 is a humanized monoclonal antibody (mAb) directed to tumor necrosis factor (TNF)-like ligand 1A (TL1A), a target associated with both intestinal inflammation and fibrosis.  

In December 2022, Prometheus announced positive results for PRA023 from ARTEMIS-UC, a Phase 2, placebo controlled, study evaluating safety and efficacy in patients with moderate to severely active UC and APOLLO-CD a Phase 2A, open-label, study evaluating safety and efficacy in patients with moderate to severe CD.

Phase 3 trials for the candidate are expected to start this year.  

“Prometheus was established to revolutionize the treatment of immune-mediated diseases through the application of a powerful precision medicine approach,” said Mark McKenna, chairman and chief executive officer of Prometheus Biosciences.

“This agreement with Merck, a leader in biopharmaceutical research and development, allows Prometheus to maximize the potential for PRA023, while continuing to apply our technology and expertise to fuel further discoveries to address the needs of patients with immune disorders.”

Alongside its lead candidate, Prometheus’ other potential target diseases include rheumatoid arthritis, psoriasis and atopic dermatitis.

Portfolio diversification

For Merck, known as MSD outside the US and Canada, the acquisition will help it diversify its portfolio as it looks towards the expiry of patents on ahead on its blockbuster cancer immunotherapy Keytruda towards the end of the decade.  

Merck will acquire Prometheus via a subsidiary for $200 per share in cash, for a total equity value of approximately $10.8bn.

“The agreement with Prometheus will accelerate our growing presence in immunology where there remains substantial unmet patient need,” said Robert M. Davis, chairman and chief executive officer, Merck. 

“This transaction adds diversity to our overall portfolio and is an important building block as we strengthen the sustainable innovation engine that will drive our growth well into the next decade.”